Systems and methods for atomic layer deposition

ABSTRACT

An atomic layer deposition (ALD) method can include pulsing a first reactant vapor into a reactor assembly. The first reactant vapor is supplied to a first reactant gas line. An inactive gas is supplied to a first inactive gas line at a first flow rate. The first reactant vapor and the inactive gas are fed to the reactor assembly by way of a first feed line. The reactor assembly is purged by supplying the inactive gas to the first inactive gas line at a second flow rate higher than the first flow rate. A first portion of the inactive gas can be fed back along a diffusion barrier portion of the first reactant gas line to provide an inert gas valve (IGV) upstream of the first inactive gas line. A second portion of the inactive gas can be fed to the reactor assembly by way of the first feed line.

BACKGROUND Field

The field relates to systems and methods for atomic layer deposition(ALD).

Description of the Related Art

Atomic Layer Deposition (ALD) is a method for growing highly uniformthin films onto a substrate. In a time-divided ALD reactor, thesubstrate is placed into reaction space free of impurities and at leasttwo different volatile precursors (reactant gases) are injected in vaporphase alternately and repetitively into the reaction space. The filmgrowth is based on self-limiting surface reactions that take place onthe surface of the substrate to form a solid-state layer of atoms ormolecules, because the reactants and the temperature of the substrateare chosen such that the alternately-injected vapor-phase precursor'smolecules react only on the substrate with its surface layer. Thereactants are injected in sufficiently high doses for the surface to bepractically saturated during each injection cycle. Therefore, theprocess is highly self-regulating, being not dependent on theconcentration of the starting materials, whereby it is possible toachieve extremely high film uniformity and a thickness accuracy of asingle atomic or molecular layer. Similar results are obtained inspace-divided ALD reactors, where the substrate is moved into zones foralternate exposure to different reactants. Reactants can contribute tothe growing film (precursors) and/or serve other functions, such asstripping ligands from an adsorbed species of a precursor to facilitatereaction or adsorption of subsequent reactants.

The ALD method can be used for growing both elemental and compound thinfilms. ALD can involve alternate two or more reactants repeated incycles, and different cycles can have different numbers of reactants.Pure ALD reactions tend to produce less than a monolayer per cycle,although variants of ALD may deposit more than a monolayer per cycle.

Growing a film using the ALD method can be a slow process due to itsstep-wise (layer-by-layer) nature. At least two gas pulses arealternated to form one layer of the desired material, and the pulses arekept separated from each other for preventing uncontrolled growth of thefilm and contamination of the ALD reactor. After each pulse, the gaseousreaction products of the thin-film growth process as well as the excessreactants in vapor phase are removed from the reaction space, or thesubstrate is removed from the zone that contains them. In time-dividedexamples, this can be achieved by pumping down the reaction space, bypurging the reaction space with an inactive gas flow between successivepulses, or both. Purging employs a column of an inactive gas in theconduits between the reactant pulses. Purging is widely employed onproduction scale because of its efficiency and its capability of formingan effective diffusion barrier between the successive pulses. Regularly,the inert purging gas is also used as a carrier gas during reactantpulses, diluting the reactant vapor before it is fed into the reactionspace.

Sufficient substrate exposure and good purging of the reaction space aredesirable for a successful ALD process. That is, the pulses should beintense enough for the substrate to be practically saturated (in theflattened portion of the asymptotic saturation curve) and purging shouldbe efficient enough to remove practically all precursor residues andundesired reaction products from the reactor. Purge times can berelatively long with respect to the precursor exposure times.

In order to accelerate the film growth process, there is a demand formethods that enable shortening of the purge periods and, thus, the pulseintervals. However, one of the most challenging factors contributing tothe process cycle times is a temporal widening of the reactant vaporpulses. Successive pulses should be kept sufficiently separated, becausethe gases may be mixed if fed with too frequent intervals due to theirfinite rise and drop times. A widening of the pulse is the result ofthree main phenomena: a pressure gradient formed between the reactantand inert gas flows, gas diffusion, and gas adsorption onto anddesorption from the surfaces of the reactor. All these effects causemixing of the reactant vapor and the inert gas, which causes long purgetimes to ensure operation under proper ALD conditions. Intravelling-wave pulsing methods, where reactants are injected intocontinuous inert carrier flows, the total pressure in the reactor feedline increases at the same time as the reactant partial pressure isincreased in the line, which causes the pulses to be widened not only bydiffusion and adsorption/desorption, but also by pressure gradientdriven flow.

Thus, there remains a continuing need for accelerating thin film growthprocesses while reducing the effects of temporal widening of thereactant vapor pulses.

SUMMARY

The systems and methods of the present disclosure have several features,no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, various features will now be discussedbriefly. After considering this discussion, and particularly afterreading the section entitled “Detailed Description,” one will understandhow the features described herein provide several advantages overtraditional gas delivery methods and systems.

An atomic layer deposition (ALD) method is disclosed. The ALD method caninclude pulsing a first reactant vapor into a reactor assembly. Thepulsing can comprise supplying the first reactant vapor to a firstreactant gas line. The pulsing can comprise supplying an inactive gas toa first inactive gas line at a first flow rate. The pulsing can comprisefeeding the first reactant vapor and the inactive gas to the reactorassembly by way of a first feed line. The ALD method can further includepurging the reactor assembly. The purging can comprise supplying theinactive gas to the first inactive gas line at a second flow rate thatis higher than the first flow rate. The purging can comprise feeding afirst portion of the inactive gas back along a diffusion barrier portionof the first reactant gas line to provide an inert gas valve (IGV)upstream of the first inactive gas line. The purging can comprisefeeding a second portion of the inactive gas to the reactor assembly byway of the first feed line.

In another embodiment, an atomic layer deposition (ALD) device isdisclosed. The ALD device can include a reactor assembly and a firstreactant gas line configured to supply a first reactant vapor from afirst reactant vapor source. The ALD device can include a first inactivegas line configured to supply an inactive gas from an inactive gassource. The ALD device can include a first feed line communicating witheach of the first reactant gas line and the first inactive gas line tosupply the first reactant vapor and the inactive gas to the reactorassembly. The ALD device can include a drain line communicating with thefirst reactant gas line upstream of the first inactive gas line. The ALDdevice can include a first valve along the first inactive gas line, thefirst valve having an open state and a closed state. The ALD device caninclude a second valve along the first inactive gas line, the secondvalve comprising an adjustable valve configured to adjustably regulategas flow through the first inactive gas line at a plurality of non-zeroflow rates.

In another embodiment, an atomic layer deposition (ALD) device isdisclosed. The ALD device can include a reactor assembly and an inactivegas distribution line configured to supply an inactive gas from aninactive gas source. The ALD device can include a flow controllerconfigured to control an amount of the inactive gas that flows along theinactive gas distribution line. The ALD device can include a pluralityof reactant gas lines communicating between a plurality of reactantvapor sources and the reactor assembly. The ALD device can include aplurality of inactive gas lines branching from the inactive gasdistribution line downstream of the flow controller, each of theinactive gas lines configured to communicate inactive gas from theinactive gas distribution line to one of the reactant gas lines. The ALDdevice can include a bypass line branching from the inactive gasdistribution line downstream of the flow controller, the bypass lineconfigured to provide fluid communication between the inactive gasdistribution line and a vacuum source.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will now be described with reference to the drawings ofseveral embodiments, which embodiments are intended to illustrate andnot to limit the invention.

FIG. 1 is a schematic system diagram of a conventional atomic layerdeposition (ALD) device.

FIG. 2 is a schematic system diagram of an ALD device, according to oneembodiment.

FIG. 3 is a schematic system diagram of an ALD device that includes aplurality of reactant gas sources, according to another embodiment.

FIG. 4 is a flowchart illustrating an ALD method, according to variousembodiments.

DETAILED DESCRIPTION

The embodiments disclosed herein can be utilized with semiconductorprocessing devices configured for any suitable gas or vapor depositionprocess. For example, the illustrated embodiments show various systemsfor depositing material on a substrate using atomic layer deposition(ALD) techniques. Among vapor deposition techniques, ALD has manyadvantages, including high conformality at low temperatures and finecontrol of composition during the process. ALD type processes are basedon controlled, self-limiting surface reactions of reactant chemicals. Ina time-divided ALD reactor, gas phase reactions are avoided by feedingthe precursors alternately and sequentially into the reaction chamber.Vapor phase reactants are separated from each other in the reactionchamber, for example, by removing excess reactants and/or reactantby-products from the reaction chamber between reactant pulses. Removalcan be accomplished by a variety of techniques, including purging and/orlowering pressure between pulses. Pulses can be sequential in acontinuous flow, or the reactor can be isolated and can backfilled foreach pulse.

Briefly, a substrate is loaded into a reaction chamber and is heated toa suitable deposition temperature, generally at lowered pressure.Deposition temperatures are typically maintained below the precursorthermal decomposition temperature but at a high enough level to avoidcondensation of reactants and to provide the activation energy for thedesired surface reactions. Of course, the appropriate temperature windowfor any given ALD reaction will depend upon the surface termination andreactant species involved.

A first reactant vapor is conducted into the chamber in the form ofvapor phase pulse and contacted with the surface of a substrate.Conditions are preferably selected such that no more than about onemonolayer of the precursor is adsorbed on the substrate surface in aself-limiting manner. Excess first reactant and reaction byproducts, ifany, are purged from the reaction chamber, often with a pulse of inertgas such as nitrogen or argon.

Purging the reaction chamber means that vapor phase precursors and/orvapor phase byproducts are removed from the reaction chamber such as byevacuating the chamber with a vacuum pump and/or by replacing the gasinside the reactor with an inert gas such as argon or nitrogen. Typicalpurging times for a single wafer reactor are from about 0.05 to 20seconds, such as between about 1 and 10 seconds, for example betweenabout 1 and 2 seconds. However, other purge times can be utilized ifdesired, such as when depositing layers over extremely high aspect ratiostructures or other structures with complex surface morphology isneeded, or when a high volume batch reactor is employed. The appropriatephase and cycle times can be readily determined by the skilled artisanbased on the particular circumstances.

A second reactant vapor is provided into the chamber where it reactswith species of the first reactant vapor bound to the surface. Excesssecond reactant vapor and gaseous by-products of the surface reactionare purged out of the reaction chamber, preferably with the aid of aninert or inactive gas. Providing the reactants alternately and purgingare repeated until a thin film of the desired thickness has been formedon the substrate, with each cycle leaving no more than a molecularmonolayer. Some ALD processes can have more complex sequences with threeor more reactant pulses alternated. Reactants can also be supplied tothe substrate in their own phases or with precursor pulses to strip orgetter adhered ligands and/or free by-product, rather than contributeelements to the film. Additionally, not all cycles need to be identical.For example, a binary film can be doped with a third element byinfrequent addition of a third reactant pulse, e.g., every fifth cycle,in order to control stoichiometry of the film, and the frequency canchange during the deposition in order to grade film composition.Moreover, while described as starting with an adsorbing reactant, somerecipes may start with another reactant or with a separate surfacetreatment, for example to ensure maximal reaction sites to initiate theALD reactions (e.g., for certain recipes, a water pulse can providehydroxyl groups on the substrate to enhance reactivity for certain ALDprecursors).

As mentioned above, each pulse or phase of each cycle is preferablyself-limiting. An excess of reactant precursors is supplied in eachphase to practically saturate the susceptible structure surfaces.Surface saturation ensures reactant occupation of all available reactivesites (subject, for example, to physical size or steric hindrancerestraints) and thus ensures excellent step coverage over any topographyon the substrate. In some arrangements, the degree of self-limitingbehavior can be adjusted by, e.g., allowing some overlap of reactantpulses to trade off deposition speed (by allowing some CVD-typereactions) against conformality. Ideal ALD conditions with reactantswell separated in time and space provide near perfect self-limitingbehavior and thus maximum conformality, but steric hindrance results inless than one molecular layer per cycle. Limited CVD reactions mixedwith the self-limiting ALD reactions can raise the deposition speed.While embodiments described herein are particularly advantageous forsequentially pulsed deposition techniques, like ALD and mixed-modeALD/CVD, the reactor assemblies disclosed herein can also be employedfor pulsed or continuous CVD processing.

Examples of suitable reactors that may be used include commerciallyavailable ALD equipment such as any of the Pulsar®, EmerALD®, Eagle®series reactors, available from ASM International of Almere, theNetherlands. Many other kinds of reactors capable of ALD growth of thinfilms, including CVD reactors equipped with appropriate equipment andmeans for alternatingly supplying the reactants, can be employed.

The ALD processes can be carried out in a reactor or reaction spaceconnected to a cluster tool in various embodiments. In a cluster tool,because each reaction space is dedicated to one type of process, thetemperature of the reaction space in each module can be kept constant,which improves the throughput compared to a reactor in which is thesubstrate is heated to the process temperature before each run. Astand-alone reactor can be equipped with a load-lock. In that case, itis not necessary to cool down the reaction space between each run. Theseprocesses can also be carried out in a reactor designed to processmultiple substrates simultaneously, e.g., a mini-batch type showerheadreactor. Still other types of reactor assemblies can be used inconjunction with the embodiments disclosed herein.

As compared with current ALD implementations, various embodimentsdisclosed herein can provide significantly higher purge flow rates andrapid increases in purge pressures, and can reduce temporal widening ofthe reactant vapor pulses. Beneficially, the embodiments disclosedherein can result in faster film growth by shortening the pulse widthsand improving pulse separation. Moreover, improving pulse separation canbeneficially reduce intermixing of the reactant vapor(s) and inactivegas(es) and can reduce contamination in the reactor assembly and in thevarious supply lines. Moreover, the inert gas valving (IGV) solutionspresented herein can be provided outside the hot zone of the reactorassembly, such that the valves used in the reactant and inactive gaslines need not be exposed to the high temperatures of the reactorassembly, thus avoiding contamination issues raised by exposing valvesto high temperatures. In addition, various embodiments disclosed hereinmay utilize a single flow controller that regulates the flow of inactivegas to multiple gas lines for multiple reactants of the system, ascompared with other implementations that utilize multiple flowcontrollers, which can further reduce system costs. Relative to use ofindividual controllers, by the addition of relatively inexpensive parts,such as needle valves and an extra line (e.g., a foreline), the systemsdescribed herein permit individual control over gas conductance inmultiple inactive gas lines to permit, for example, higher inert gasflow during purge states and faster activation of IGV to shut downreactant flow during purging. The embodiments disclosed herein cantherefore significantly improve the productivity of the ALD process,resulting in reduced processing and assembly costs.

FIG. 1 is a schematic system diagram of a conventional atomic layerdeposition (ALD) device 1 utilizing inert gas valving (IGV). The ALDdevice 1 can comprise an inert or inactive gas source 2 configured tosupply an inactive gas to an inactive gas line 6. The inactive gas cancomprise a gas that does not react with reactant vapor(s) or thesubstrate upon which the thin film is to be deposited. The inactive gasalso serves to prevent reactions between the substances of the differentreactant groups, for example by providing a diffusion barrier in thefeed line to the reactor assembly between reactant phases. Any suitabletype of inactive gases may be used in the embodiments disclosed herein,including, e.g., inert gases, such as nitrogen gas, and noble gases,e.g., argon. The inactive gas may also be an inherently reactive gas,such as hydrogen gas serving to prevent undesirable reactions, e.g.,oxidization reactions, from occurring on the substrate surface,depending upon relative reactivity with the other reactants.

A flow controller 12 can control the amount of inactive gas (e.g., theflow rate) that is supplied to the inactive gas line 6. In variousembodiments, the flow controller 12 can comprise a Mass Flow Controller(MFC), which can be configured to control an amount or flow rate of theinactive gas that is supplied to the inactive gas line 6. In otherembodiments, other types of flow controllers may be used.

A reactant vapor source 3 can be configured to supply a vaporizedprecursor or reactant vapor to a reactant gas line 7. A reactant gasvalve 14 can be configured to turn on or off the flow of reactant vaporthrough the reactant gas line 7 from the reactant gas source 3. Thereactant gas valve 14 can be any suitable type of valve, including,e.g., solenoid-type valves, pneumatic valves, piezoelectric valves, etc.The reactant gas source 3 can provide reactant vapor. The reactant vaporcan comprise a vaporizable material capable of reacting with thesubstrate surface or a previously reactant left on the substratesurface. The reactants may be naturally solids, liquids or gases understandard conditions, and accordingly may the reactant vapor source 3 mayinclude a vaporizer. The reactant vapor source 3 may also include flowcontrol device(s) upstream of the reactant gas valve 14. For vaporizedreactants, the flow controller may control the flow of inert carrier gasthrough the vaporizer.

The term “metallic reactants” refers generally to metallic compounds,which may comprise elemental metals. Examples of metallic reactants arethe halogenides of metals including chlorides and bromides, forinstance, and metal-organic compounds such as the thd(2,2,6,6-tetramethyl-3,5-heptanedione) complex compounds and Cp (—C5H5,cyclopentadienyl) compounds. More particular examples of metallicreactants include Zn, ZnCl₂, TiCl₄, Ca(thd)₂, (CH₃)₃Al and (Cp)₂Mg.Nonmetallic reactants can comprise compounds and elements capable ofreacting with metallic compounds. Nonmetallic reactants can comprisewater, sulfur, hydrogen sulfide, oxygen, ozone and ammonia and as wellas plasmas of different nonmetallic reactants such as hydrogen orhydrogen/nitrogen mixture. Still other types of vapor reactants may beused.

As shown in FIG. 1, a backsuction or drain line 9 can fluidly connect tothe reactant gas line 7 at a junction 11. The drain line 9 can befluidly connected to a vacuum source 5, and a flow restrictor 13 can beprovided along the drain line 9 to restrict the flow of gases evacuatedalong the drain line 9. The flow restrictor 13 can be a passive deviceor a valve that does not fully close in operation. During operation, thevacuum source 5 can apply suction forces to the reactant gas line 7 atthe junction 11, which may be disposed downstream of the reactant gasvalve 14. In various embodiments, the vacuum source 5 may be activatedduring both dose states (in which reactant vapor(s) are supplied to thesubstrate) and purge states (in which the reactor assembly is purged ofexcess reactants and byproducts).

The inactive gas line 6 can join with the reactant gas line 7 at ajunction 10. In various embodiments, when the reactant gas valve 14 isopen, the vapor pressure of the reactant vapor can be sufficiently highso as to drive the reactant vapor along the reactant gas line 7. Inother embodiments, the reactant vapor can be actively driven along thereactant gas line 7, e.g., the reactant vapor source 3 can include aninactive carrier gas supply to drive the reactant vapor along thereactant gas line 7. The inactive gas flow can be regulated along theinactive gas line 6 by the flow controller 12. During a pulsing ordosing state, the inactive gas can merge with the reactant vapor at thejunction 10, and the merged vapors can be fed along a feed line 8 to areactor assembly 4. In various arrangements, the reactor assembly 4 caninclude a processor chamber comprising a substrate support configured tosupport a substrate (such as a wafer). In some arrangements, a mixer isprovided along the feed line 8 mix the reactant vapor with the inert gasflow prior to delivery to the process chamber. In other arrangements, nomixer is used, and the individual feed line(s) 8 may deliver thereactant and inactive gases to the process chamber. The ALD device 1 mayalso include baffles or expansion plenums along the feed line 8 tospread the flow of the reactant vapor and inert gases across thesubstrate.

During a dose state of the ALD device 1 shown in FIG. 1, the reactantgas valve 14 can be opened to feed reactant vapor to the reactant gasline 7. The total flow rate of gases into the reactor assembly 4 can bedetermined based on an inactive gas flow rate F_(I) along the inactivegas line 6, a reactant vapor flow rate F_(R) along the reactant gas line7, and a drain flow rate F_(D) along the drain line 9 from the junction11 to the vacuum source 5. For example, the total flow into the reactorassembly 4 along the feed line 8 can be given by F=F_(I)+F_(R)−F_(D). Inthe dose state, a pressure P_(A) along the reactant gas line at thejunction 11 is greater than a pressure P_(B) at the junction 10 betweenthe inactive gas line 6 and the reactant gas line 7. In the dose state,therefore, reactant vapor from the reactant gas line 7 and inactive gasfrom the inactive gas line 6 merge into the feed line 8 and are fed intothe reactor assembly. In addition, a small portion of the reactant vaporis suctioned along the (restricted) drain line 9 by the vacuum source 5.

After a dose state of feeding reactant vapor to the reactor assembly 4,it can be important to purge the process chamber with inactive gas toremove all or substantially all excess reactant gases, byproducts, andother undesirable materials in the process chamber after dosing toprevent gas phase reactions with subsequent reactants. During a purgestate or process, the reactant gas valve 14 can be closed in order tostop the flow of reactant vapor to the reactant gas line 7. Afterclosing the reactant gas valve 14, the pressure P_(A) at the junction 11is less than the pressure P_(B) at the junction 10. The pressuredifferential can cause residual precursor material and a portion of theinactive gas to flow back through the drain line 9 towards the vacuumsource 5. Because the reactant gas valve 14 is closed during purging,only the inactive gas can flow along the feed line 8 to purge thereactor assembly 4 of undesirable species. This creates a backward flowof inactive gas along a diffusion barrier portion 26 of the reactant gasline 7 disposed between junction 10 and junction 11, which serves as adiffusion barrier against continued diffusion or flow of residualreactant in the reactant gas line 7. This diffusion barrier serves asthe “inert gas valve” within the hot zone of the reactor, close to thereaction chamber, while actual valves and controllers 12, 14 can remainoutside the hot zone and not subject to the wear of high temperaturesand consequent contaminants. After purging, the process can repeat byinitiating another dose state (typically of another reactant vapor)followed by another purge state, until the thin film has been grown onthe substrate in the process chamber to a desired thickness anduniformity.

Although only one reactant vapor source 3 and one inactive gas source 2are illustrated in FIG. 1, it should be appreciated that, a plurality ofreactant vapor sources 3 and/or inactive gas sources 2 can be providedin an ALD device. In such arrangements, for each inactive gas line 6that is provided, a corresponding flow controller 12 may also beprovided to regulate the flow of inactive gas through that line 6.Similarly, for each reactive gas line 6, a corresponding reactant gasvalve 14 can be provided.

As explained above, it can be important to provide high throughput inthe ALD device 1 without contamination of the substrate and or reactorassembly 4. Accordingly, it can be important to ensure that the reactantvapors do not undesirably intermix with one another or with the inactivegas used in the purge state. Intermixing can occur due to a pressuregradient between the reactant and inactive gases, and can causecontamination of the reactor assembly 4 and/or substrate. Widening thepulses and/or increasing the pulse separation, however, can undulyincrease the overall processing time used to form the thin film. Theindividual flow controller 12 along the inactive gas line permitsincreasing inert gas flow in the illustrated IGV system during purgestates, which can advantageously result in faster purge, a betterdiffusion barrier and faster IGV shut off of the reactant. However, flowcontrollers, such as mass flow controllers, are quite costly andproviding such control on each of several reactant gas lines multipliesthe cost.

FIG. 2 is a schematic system diagram of an ALD device 1, according toone embodiment. Unless otherwise noted, components in FIG. 2 may be thesame as or generally similar to like-numbered components of FIG. 1. Aswith FIG. 1, the device 1 of FIG. 2 includes an inactive gas source 2configured to supply an inactive gas to an inactive gas line 6, and areactant vapor source 3 configured to supply a reactant vapor to areactant gas line 7. Further, the device 1 can comprise a feed line 8configured to supply the reactant vapor and the inactive gas to areactor assembly 4. As explained above, the reactor assembly can 4comprise a mixer connected to multiple reactant sources and a processchamber downstream of the mixer. In other embodiments, the feed line(s)8 can be fed directly to the processor chamber without an interveningmixer.

Furthermore, as with FIG. 1, the reactant gas valve 14 can be a shut-offvalve to allow or prohibit the flow of reactant vapor from the reactantvapor source 3 to the reactant gas line 7. As noted with respect to FIG.1, a mass flow controller may also be associated with the reactant vaporsource 3, upstream or downstream of the pulsing valve reactant gas valve14. The reactant gas line 7 can connect to the inactive gas line 6 atthe junction 10. As explained above, during a dosing or pulsing state,reactant vapor can be entrained with the carrier inactive gas to feedreactant and inactive carrier gas to the reactor assembly 4 along thefeed line 8. During a purging state, only the inactive gas may flowthrough the feed line 8 to the reactor assembly 4 to purge the reactorassembly 4 of undesirable species (e.g., excess reactant, byproducts,etc.).

Unlike the arrangement of FIG. 1, however, in FIG. 2, a bypass line(e.g., a foreline 15) can fluidly connect to the inactive gas line 6downstream of the flow controller 12 between the flow controller 12 andthe junction 10. In other embodiments, however, the bypass line may belocated at other portions of the device 1. The foreline 15 can be influid communication with the vacuum source 5 (or a different vacuumsource), which can apply suction forces to the inactive gas line 6 at ajunction 20 between the foreline 15 and the inactive gas line 6. Asshown in FIG. 2, a first shutoff valve 16 a and a first adjustable valve17 a can be provided along and in fluid communication with the foreline15. In various embodiments, the first shutoff valve 16 a can comprise avalve having an open state and a closed state. In the open state, gas ispermitted to freely flow through the valve 16 a. In the closed state,gas is blocked from flowing through the valve 16 a. In variousembodiments, the shutoff valve 16 a can have only two states, e.g.,fully open or fully closed. In the illustrated embodiment, for example,the first shutoff valve 16 a comprises a pneumatic valve operablycontrolled by a control system 32, which can comprise processingelectronics configured to electronically activate the pneumatic valve.In other embodiments, however, the shutoff valve 16 a can be adjustableor allow a trickle flow in the “closed” state.

The first adjustable valve 17 a can comprise an adjustable valveconfigured to adjustably regulate gas flow through the foreline 15 at aplurality of non-zero flow rates. For example, in some embodiments, theadjustable valve 17 a can adjust flow rates along a continuum ofpossible flow rates. In various embodiments, the adjustable valve 17 acan be set at a predetermined set point that creates a desired pressuregradient across the valve 17 a. In the illustrated embodiment, the firstadjustable valve 17 a can comprise a needle valve that can be adjustedmanually or automatically to control a flow rate of gases beingsuctioned through the foreline 15. For example, in various embodiments,the first adjustable valve 17 a can be set to a predetermined set pointthat provides a desirable pressure gradient across and/or flow ratethrough the valve 17 a.

Further, as shown in FIG. 2, a drain line 9 can connect to the reactantgas line 7 at a junction 11. The drain line 9 can fluidly connect to theforeline 15 at a junction 18. A flow restrictor 13 can also be providedalong the drain line 9 in some embodiments. When activated, the vacuumsource 5 can also apply suction forces to the reactant line 7 at thejunction 11 so as to draw gases back towards the vacuum source 5.

In addition, as shown in FIG. 2, the inactive gas line 6 can include asecond shutoff valve 16 b and a second adjustable valve 17 b disposedbetween the junction 20 with the foreline 15 and the junction 10 withthe reactant gas line 7. A pressure transducer 19 can be providedupstream of one or both the valves 16 b, 17 b to measure the pressure ofthe inactive gas flowing through the inactive gas line 6 upstream of thevalves 16 b and/or 17 b. As with the first shutoff valve 16 a, thesecond shutoff valve 16 b can comprise a valve having an open state anda closed state. In the open state, gas is permitted to freely flowthrough the valve 16 b. In the closed state, gas is blocked from flowingthrough the valve 16 b. In various embodiments, the shutoff valve 16 bcan have only two states, e.g., fully open or fully closed. In theillustrated embodiment, for example, the second shutoff valve 16 bcomprises a pneumatic valve operably controlled by the control system32, which can comprise processing electronics configured toelectronically activate the pneumatic valve. In other embodiments,however, the shutoff valve 16 b can be adjustable.

Similarly, the second adjustable valve 17 b can comprise an adjustablevalve configured to adjustably regulate gas flow through the inactivegas line 6 at a plurality of non-zero flow rates. For example, in someembodiments, the adjustable valve 17 b can adjust flow rates along acontinuum of possible flow rates. In various embodiments, the adjustablevalve 17 b can be set at a predetermined set point that creates adesired pressure gradient across the valve 17 b. In the illustratedembodiment, the second adjustable valve 17 b can comprise a needle valvethat can be adjusted manually or automatically to control a flow rate ofgases being suctioned through the inactive gas line 6. For example, invarious embodiments, the second adjustable valve 17 b can be set to apredetermined set point that provides a desirable pressure gradientacross and/or flow rate through the valve 17 b.

As explained above, it can be important in ALD processes to increasethroughput, reduce processing times, improve the diffusion barrier, andreduce inert gas valving (IGV) shut-off speeds (e.g., the speed at whichthe process is switched from dosing to purging states, and vice versa).Various embodiments disclosed herein accomplish these objectives bysignificantly increasing the inactive gas flow rate F_(I) along theinactive gas line 6 during purging of the reactor assembly 4. Increasingthe inactive gas flow rate F_(I) can result in a very rapid increase inpressure, which can accordingly result in a faster purge process, animproved diffusion barrier, and faster IGV switching speeds.

During a dose state or process, the first shutoff valve 16 a and thefirst reactant valve 14 can be opened. The second shutoff valve 16 b isalso open during the dose state. Indeed, in various embodiments, thesecond shutoff valve 16 b remains open during both the dose state andthe purge state, such that some amount of inactive gas flows through theinactive gas line 6 during both dosing and purging. In the dose state,with the first and second shutoff valves 16 a, 16 b open, the firstadjustable valve 17 a can be set to provide a significantly greaterconductance along the foreline 15 compared to the conductance along theinactive gas line 6 that is afforded by the setting of the secondadjustable valve 17 b. Accordingly, a majority of the inactive gas fromthe inactive gas source 2 and its flow controller 12 flows towards thevacuum source 5 along the foreline 15, which thus serves as a bypass orvent during dosing. A minority of the inactive gas can be fed throughthe inactive gas line 6 to the junction 10 with the reactant gas line 7.Advantageously, the set points of the adjustable valves 17 a, 17 b canbe selected such that, during dosing, a majority of inactive gas flowsthrough the foreline 15 and a minority of inactive gas flows through theinactive gas line 6 to the junction 10. For example, in someembodiments, the first adjustable valve 17 a can be set to be more openthan the second adjustable valve 17 b such that, when the first shutoffvalve 16 a is opened, more inactive gas flows through the foreline 15than through the inactive gas line 6. However, the apparatus is not solimited, and advantages can be obtained even if less than the majorityof the inactive gas flow is fed through the foreline 15, as will beunderstood from the description of transition to purge states describedbelow.

In the dose state, the pressure P_(A) along the reactant gas line 7 atthe junction 11 is greater than a pressure P_(B) at the junction 10between the inactive gas line 6 and the reactant gas line 7. In the dosestate, therefore, reactant vapor from the reactant gas line 7 and theinactive gas from the inactive gas line 6 merge into the feed line 8 andare fed into the reactor assembly 4. In addition, a relatively smallportion of the reactant vapor is suctioned backwards along the drainline 9 by the vacuum source 5 through the flow restrictor 13. Forexample, in some embodiments between about 3% and about 20% of thereactant vapor may be suctioned backwards along the drain line. Invarious embodiments, for example, between about 3% and about 5% of thereactant vapor can be suctioned backwards for a low vapor solid source(e.g., hafnium chloride). In some embodiments, between about 10% andabout 20% of the reactant vapor can be suctioned backwards forrelatively high vapor sources, such as water or ozone. In variousembodiments, the amount suctioned backwards can depend on the size ofthe flow restrictor 13. The merged inactive and reactant gases pass intothe processing chamber and react with the substrate to form a thin film.

After dosing, the processing chamber can be purged by closing thereactant gas valve 14 and the first shutoff valve 16 a. As explainedabove, the second shutoff valve 16 b can remain open during both dosingand purging. When the first shutoff valve 16 a is closed, all (orsubstantially all) the inactive gas suddenly is driven through theinactive gas line 6, and no (or substantially no) inactive gas passesthrough the foreline 15. The sudden, increased flow of inactive gasthrough the inactive gas line 6 rapidly increases the flow rate andpressure of the inactive gas (e.g., the pressure P_(B) at the junction10 between the reactant gas line 7 and the inert gas line 6) duringpurging. The increased inactive gas flow through the inactive gas line 6and the feed line 8 to the reactor assembly 4 to purge the reactorassembly 4 of undesirable species. After purging, another dosing state(which may comprise a different precursor or reactant vapor) can beimplemented by opening the valves 14, 16 a. The process can besequentially repeated until the thin film on the substrate has reachedthe desired thickness and/or uniformity.

The increased flow rate and pressure of the inactive gas beneficiallyreduces the purge time, increases IGV switching speeds (e.g., thetransition from dose state to purge state), and can shorten thepulsewidth and/or pulse interval of reactant gases. The diffusionbarrier between the reactant and/or inactive gases can be improved dueto the significantly higher pressure P_(B) at the junction 10. As aresult, ALD processing times and reactor system contamination can besignificantly reduced and/or dilution of reactant vapors during dosingcan be reduced. Furthermore, the IGV processes disclosed herein, e.g.,the switching between dosing and purging states, may be regulated atleast in part by the diffusion barriers provided by the pulsing andpurging techniques disclosed herein. The physical valves 14, 16 a, 16 b,17 a, 17 b and flow controller 12, 14 can advantageously be providedoutside the hot zone created by the high processing temperaturesassociated with the reactor assembly 4. Thus, the valves 14, 16 a-16 b,and 17 a-17 b may be unaffected by the high processing temperature ofthe reactor assembly 4, and need not utilize specialized valves used inhigh temperature environments. At the same time, the diffusion barrierportion 26 between junction 10 and junction 11, serving as an inert gasvalve, operates within the hot zone close to the reaction chamber 4,permitting rapid switching with minimal continued diffusion of reactantto the reaction chamber after the reactant flow is stopped.

FIG. 3 is a schematic system diagram of an ALD device 1 that includes aplurality of reactant gas sources 3 a-3 d, according to anotherembodiment. Unless otherwise noted, components in FIG. 2 may be the sameas or generally similar to like-numbered components of FIG. 1. Forexample, as with FIG. 2, in FIG. 3, the device 1 can comprise aninactive gas source 2 and a flow controller 12 configured to supplyinactive gas to an inactive gas distribution line 6. Further, a foreline15 can connect with the inactive gas distribution line 6 at a junction20 a to serve as a selective bypass of the inactive gas distributionline 6 to a vacuum source 5. The first shutoff valve 16 a and the firstadjustable valve 17 a can be provided along the foreline 15.

Unlike the embodiment of FIG. 2, in FIG. 3, a plurality of reactantvapor sources 3 a-3 d can be provided. Each reactant vapor source 3 a-3d can contain vaporized reactant gases, which may differ from oneanother. Beneficially, using multiple (e.g., two, three, four as shown,five, six, etc.) reactant sources can enable the formation of morecomplex compounds on the substrate and/or redundant supplies of reactantto permit recharging reactant sources without halting deposition. Eachreactant vapor source 3 a-3 d is connected to a corresponding reactantgas line 7 a-7 d. Corresponding reactant gas valves 14 a-14 d can beconfigured to allow or prohibit the respective gas flows from thereactant gas sources 3 a-3 d to the reactant gas lines 7 a-7 d.Furthermore, for each reactant gas line 7 a-7 d, corresponding drainlines 9 a-9 d can connect to the reactant gas lines 7 a-7 d at junctions11 a-11 d. Corresponding flow restrictors 13 a-13 d can be providedalong the drain lines 9 a-9 d between the junctions 11 a-11 d and thejunctions 18 a-18 d along the foreline 15.

Furthermore, in FIG. 3, a plurality of inactive gas lines 6 a-6 d canfluidly connect to (and branch off from) the inactive gas distributionline 6. The plurality of inactive gas lines 6 a-6 d can connect to theinactive gas distribution line 6 at corresponding junctions 20 b-20 e asshown in FIG. 3. As with FIG. 2, each inactive gas line 6 a-6 d cancomprise corresponding shutoff valves 16 b-16 e and correspondingadjustable valves 17 b-17 e. As with FIG. 2, the shutoff valves 16 a-16e can comprise valves having an open state and a closed state. In theopen state, gas is permitted to freely flow through the valves 16 a-16e. In the closed state, gas is blocked from flowing through the valves16 a-16 e. In various embodiments, the shutoff valves 16 a-16 e can haveonly two states, e.g., fully open or fully closed. In the illustratedembodiment, for example, the shutoff valves 16 a-16 e comprise pneumaticvalves operably controlled by the control system 32, which can compriseprocessing electronics configured to electronically activate thepneumatic valve. In other embodiments, however, the shutoff valves 16a-16 e can be adjustable or allow a trickle flow in the “closed” state.

The adjustable valves 17 a-17 e can be configured to adjustably regulategas flow therethrough at a plurality of non-zero flow rates. Forexample, in some embodiments, the adjustable valves 17 a-17 e can adjustflow rates along a continuum of possible flow rates. In variousembodiments, the adjustable valves 17 a-17 e can be set at predeterminedset points that create desired pressure gradients across the valves 17a-17 e. In the illustrated embodiment, the adjustable valves 17 a-17 ecan comprise needle valves that can be adjusted manually orautomatically to control flow rates of gases flowing therethrough. Forexample, in various embodiments, the adjustable valves 17 a-17 e can beset to different predetermined set points to control the relative flowof gases through the foreline 15 and through the inactive gas lines 6a-6 d.

During a dose state of a first reactant from the first reactant source 3a, the first reactant valve 14 a can be opened, and the first shutoffvalve 16 a of the foreline 15 can be opened (e.g., pneumatically in someembodiments). During the dose state, the shutoff valves 16 b-16 e alongthe respective inactive gas supply lines 6 a-6 d may remain open (e.g.,fully open) during the entire deposition process, in some embodiments.For example, the shutoff valves 16 b-16 e can remain open during dosingof any and/or all reactant vapors, as well as during purging. In otherembodiments, however, one or more of the shutoff valves 16 b-16 e can beclosed during dosing and/or purging, e.g., if the associated reactantvapor is not being used in the deposition procedure.

When the first shutoff valve 16 a along the foreline 15 is opened, asignificant amount (for example, majority) of the inactive gas can flowthrough the foreline 15 towards the vacuum source 5, thus bypassing theinactive gas lines 6 a-6 d. Thus, less than all of the inactive gasmetered by the flow controller 12 (for example, a minority of theinactive gas flow) can flow through the respective inactive gas lines 6a-6 d to the respective junctions 10 a-10 d with the reactant lines 7a-7 d. As explained in connection with FIG. 2, to set the relativeamount of inactive gas flow through the foreline 15 during dosing, thefirst adjustable valves 17 a-17 e can be set at predetermined setpoints. For example, to set a majority of inactive gas flow through theforeline 15 during dosing, the first adjustable valve 17 a along theforeline 15 can be set to provide more flow conductance than the totalof the other adjustable valves 17 b-17 e. In such a manner, therefore,when the first shutoff valve 16 a along the foreline 15 is opened, asignificant amount (e.g., most) of the inactive gas can be suctionedinto the foreline 15 rather than being driven into the respectiveinactive gas lines 6 a-6 d. As an example, the adjustable valves 17 a-17e and the sizes of the gas lines 15, 6, 6 a-6 d can be selected suchthat, during dosing, between about 40% and 80% of the inactive gas flowsthrough the foreline 15, e.g., between about 50% and 75% of the inactivegas in various embodiments.

For pulsing of the first reactant vapor from the first reactant source,for example, as explained above, the pressure P_(B) at the junction 10with the first inactive gas line 6 a can be less than the pressure P_(A)at the junction 11 a between the reactant gas line 7 a and the drainline 9 a, due to a relatively small amount of inactive gas flow throughthe inactive gas line 6 a. The first reactant vapor (which may includecarrier gas that can be the same or different from the inactive gas) canmerge with the inactive gas at the junction 10 a, and the mergedreactants and inactive gases can be fed to the reactor assembly 4 alongfeed line 8 a. In the embodiment of FIG. 3, the reactor assembly 4comprises a mixer 22 disposed upstream of and fluidly connected with aprocessing chamber 23 by way of feed line 8 e, which can encourage moreeven mixing of the reactant vapor gas along feed line 8 a with theinactive gas supplied through all of the active feed lines 8 a-8 d. Ofcourse, for a two-reactant ALD sequence, two of the reactant lines 7 a,7 b and corresponding inactive gas lines 6 a, 6 b can be active (valves16 b, 16 c open while reactant valve 14 a and 14 b are pulsed) while twoof the reactant lines 7 c, 7 d and corresponding inactive gas lines 6 c,6 d are closed (valves 14 c, 14 d, 16 d, 16 e can be closed). The mixedgases can be fed to the processing chamber from the mixer 22 along thefeed line 8 e. As noted that, during pulsing of the first reactant vaporthrough the first feed line 8 a, inactive gases may also flow (atrelatively low flow rates) through the respective feed lines 8 b-8 d. Insome embodiments, the different reactants from the reactant vaporsources 3 a-3 d may be fed to the reactor assembly 4 sequentially, e.g.,during sequentially alternated dose states with intervening purgestates. In other embodiments, operating in CVD mode or a hybrid CVD/ALDmode, more than one reactant may be fed to the reactor assembly 4simultaneously (or substantially at the same time).

After pulsing the first reactant vapor to the reactor assembly 4 throughthe first feed line 8 a, the reactor assembly 4 can be purged withinactive gas to remove excess reactant, byproducts, and/or otherundesirable materials. In the purge state, the reactant gas valve 14 a(and any other open reactant gas valves) and the first shutoff valve 16a are closed (e.g., pneumatically). As explained above, the inactive gasshutoff valves 16 b-16 e (at least those connected to active reactantlines 7 for the recipe) can remain open during both dosing and purging.When the first shutoff valve 16 a is closed, all (or substantially all)the inactive gas suddenly is driven through the inactive gasdistribution line 6, and no (or substantially no) inactive gas passesthrough the foreline 15. The inactive gas flowing through the inactivegas distribution line 6 can be distributed to the respective inactivegas lines 6 a-6 d. The sudden, increased flow of inactive gas throughthe inactive gas lines 6 a-6 d rapidly increases the flow rate andpressure of the inactive gas (e.g., the pressure P_(B) at the junctions10 a-10 d between the reactant gas lines 7 a-7 d and the inert gas lines6 a-6 d) during purging. The rapidly-flowing inactive gas flows backwardthrough the drains 9 a-9 d to form effective diffusion barriers atrespective diffusion barrier portions 26 a-26 d between the respectivejunctions 10 a-10 d and 11 a-11 d, and through the inactive gas lines 6a-6 d and the feed lines 8 a-8 d to the reactor assembly 4 to purge thereactor assembly 4 (e.g., the mixer 22 and/or process chamber 23) ofundesirable species. After purging, another dosing state (which maycomprise a different precursor or reactant vapor) can be implemented byopening the second reactant valve 14 b and the shutoff valve 16 a. Theprocess can be sequentially repeated until the thin film on thesubstrate has reached the desired thickness and/or uniformity.

As explained above in relation to FIG. 2, the increased flow rate andpressure of the inactive gas beneficially reduces the purge time,increases IGV switching speeds (e.g., the transition from dose state topurge state), increases the effectiveness of the IGV diffusion barrier(e.g., in the diffusion barrier portions 26 a-26 d), and can shorten thepulsewidth and/or pulse interval of reactant gases. The diffusionbarrier between the reactant and/or inactive gases can be improved dueto the significantly higher pressure P_(B) at the junctions 10 a-10 d.As a result, ALD processing times and reactor system contamination canbe significantly reduced. Furthermore, the IGV processes disclosedherein, e.g., the switching between dosing and purging states, may beregulated at least in part by the diffusion barriers provided by thepulsing and purging techniques disclosed herein. The IGV processes canadvantageously be provided outside the hot zone created by the highprocessing temperatures associated with the reactor assembly 4. Thus,the valves 14 a-14 d, 16 a-16 e, and 17 a-17 e may be unaffected by thehigh processing temperature of the reactor assembly 4, and need notutilize specialized valves used in high temperature environments.

While in some arrangements, multiple flow controllers (such as flowcontrollers 12) may be used to control the flow of inactive gases alongthe inactive gas lines. In such arrangements, for example, each inactivegas line may utilize an associated, separate flow controller (such as anMFC). However, the embodiment shown in FIG. 3 utilizes only a singleflow controller 12 to regulate the flow of inactive gas for the entiredevice 1. By utilizing only one flow controller, the overall expense ofthe ALD device 1 may be significantly reduced, as compared with devicesthat utilize multiple flow controllers for the inactive gas. Forexample, for IGV on four separate reactant lines, the illustratedarrangement can employ one mass flow controller (MFC) at flow controller12 and five needle valves for adjustable valves 17 a-17 d. As comparedto four MFCs, the embodiment of FIG. 3 can provide individual controlover relative flow rates during dosing and purging for one third thecost or less.

Example Implementations of ALD Device

Table 1 illustrates a first example of adjustable valve 17 a-17 e setpoints, based on the system of FIG. 3, that can be used to improve purgespeed and achieve the other aforementioned advantages associated withthe disclosed embodiments. The parameters listed in Table 1 werecalculated based on the flow controller 12 providing a flow rate of 2000sccm for the inactive gas through the inactive gas distribution line 6and assumes four active reactant gas lines 7 a-7 d. For the initialcalibration of a particular valve 17 a-17 e, the pressure set pointvalues referenced in Row 1 are the pressures as measured by the pressuresensor 19 when every other adjustable valve is closed. For example, theset point pressure of 700 Torr for valve 17 b reflects the pressuremeasured by the sensor 19 when valve 17 b is set at a particularpredetermined set point, and the other valves 17 a and 17 c-17 e areclosed. The calibration can be repeated for the other valves 17 c-17 e.

TABLE 1 Example parameters for uniform distribution of inactive gasflow. Valve 17a Valve 17b Valve 17c Valve 17d Valve 17e (Foreline (Gas(Gas (Gas (Gas 15) line 6a) line 6b) line 6c) line 6d) Pressure Set 90700 700 700 700 Point (Torr) Flow Rate 1320 170 170 170 170 During DoseState (valve 16a open) (sccm) Flow Rate 0 500 500 500 500 During PurgeState (valve 16a closed) (sccm)

The example shown in Table 1 illustrates the change in flow ratesthrough the gas lines 6 a-6 d as the device is switched from dosing topurging. In Table 1, the valves 17 b-17 e have been set to allowrelatively uniform flow of inactive gases through the inactive gas lines6 a-6 d. As explained above, the first valve 17 a of the foreline can beset at a pressure set point that is significantly more open than thecombined conductance through the inactive gas lines 6 a-6 d, in someembodiments. Thus, during dosing, the shutoff valve 16 a is opened, anda portion (e.g., a majority in some arrangements) of the inactive gas(1320 sccm) flows through the foreline 15. Another portion (e.g., aminority in some arrangements) of the inactive gas flows through eachinactive gas line 6 a-6 d (170 sccm in each line). When the device isswitched to the purge state (e.g., by closing the valve 16 a), theflowrate through the foreline 15 drops to zero (or in some embodiments atrickle), and this additional inactive gas is routed evenly to therespective inactive gas lines 6 a-6 d because adjustable valves 17 b-17e have the same settings in this example. As shown in Table 1, the flowthrough each inactive gas line 6 a-6 d increased from 170 sccm duringdosing to 500 sccm during purging, e.g, an almost threefold increase inflow rate. The significantly increased flow during purging cansignificantly reduce processing times and can improve the diffusionbarrier, as explained herein.

Table 2 illustrates a second example of adjustable 17 a-17 e set points,based on the system of FIG. 3, that can increase purge flow for theadjustable valves 17 b and 17 c associated with the second and thirdinactive gas lines 6 b, 6 c, respectively. In some processes, forexample, the user may desire to preferentially increase purging throughinactive gas lines 6 b, 6 c as compared with the inactive gas lines 6 a,6 d. As with Table 1, the values of Table 2 are associated with a flowrate of 2000 sccm of inactive gas provided by the flow controller 12 tothe inactive gas distribution line 6.

TABLE 2 Example parameters for preferential purge flow through inactivegas lines 6b, 6c. Valve 17a Valve 17b Valve 17c Valve 17d Valve 17e(Foreline (Gas (Gas (Gas (Gas 15) line 6a) line 6b) line 6c) line 6d)Pressure Set 90 365 900 900 365 Point (Torr) Flow Rate 1182 291 118 118291 During Dose State (valve 16a open) (sccm) Flow Rate 0 289 711 711289 During Purge State (valve 16a closed) (sccm)

As shown in Table 2, the set points of valves 17 c, 17 d can be set athigher pressure set points as compared with the valves 17 b, 17 e.Increasing the pressure set points can correspond to creating anincreased pressure gradient in the particular valve. As shown in Table2, this increased pressure gradient can significantly increase the purgeflow rates through gas lines 6 b, 6 c. For example, as shown in Table 2,for each of lines 6 b, 6 c, the dosing flow rate of 118 sccm can besubstantially increased to 711 sccm for purging, e.g., an approximatelysixfold increase in flow rate. By contrast, the flow rates through thelines 6 a, 6 d do not appreciably change as the device is switched fromdosing to purging. For example, for the unused gas lines 6 a, 6 d, thesetting of the valves 17 a, 17 d may allow for less of a pressureregulation shift from the dosing to purge states, such that most of thepressure regulation shift may occur on the used gas lines 6 b, 6 c.

Table 3 illustrates a third example of adjustable 17 a-17 e set points,based on the system of FIG. 3, that can further increase purge ratesthrough inactive gas lines 6 b, 6 c. For example, in some processsequences, one or more of the reactant gas sources may not be used. Insuch arrangements, the shutoff valve associated with the inactive gasline that feeds into the associated reactant gas line may be closed. Inthe example of Table 3, the first reactant gas source 7 a is not beingused, and the shutoff valve 16 b associated with the inactive gas line 6a is closed. Shutting off the shutoff valve 16 b can beneficially causemore inactive gas to flow through the gas lines 6 b, 6 c, as comparedwith the example shown in Table 2. For example, since gas line 6 a isshut off in this example, the additional inactive gas flow can flowthrough gas lines 6 b, 6 c. The flow of inactive gas through gas line 6d does not appreciably increase because the restrictions in the valves17 c, 17 d permit more flow through the gas lines 6 b, 6 c, than doesthe valve 17 e for gas line 6 d.

TABLE 3 Example parameters for preferential purge flow through inactivegas lines 6b, 6c with shutoff valve 16b closed. Valve 17a Valve 17bValve 17c Valve 17d Valve 17e (Foreline (Gas (Gas (Gas (Gas 15) line 6a)line 6b) line 6c) line 6d) Pressure Set 90 N/A 900 900 365 Point (Torr)Flow Rate 1383 0 138 138 341 During Dose State (valve 16a open) (sccm)Flow Rate 0 0 831 831 338 During Purge State (valve 16a closed) (sccm)

FIG. 4 is a flowchart illustrating an ALD method 40, according tovarious embodiments. The method 40 begins in a decision block 41 todetermine whether a dose of reactant vapor is to be supplied to thereactor assembly. If the decision is no, then the method 40 ends. If thedecision is yes, then the method 40 moves to a block 42 to supply areactant vapor to a reactant line. As explained herein, a reactant gasvalve can be switched to allow the flow of reactant vapor to thereactant gas line. In some embodiments, the vapor pressure of thereactant vapor can be sufficiently high so as to flow through thereactant gas line when the valve is opened. In other embodiments, aninactive carrier gas can flow through a portion of the reactant vaporsource to drive the reactant vapor along the reactant gas line. In someembodiments, the ALD device comprises multiple reactant vapor sourcesand multiple associated reactant gas lines.

Moving to a block 43, inactive gas is supplied to inactive gas line(s)at first flow rate(s). As explained herein, a flow controller, such asan MFC, can be used to regulate the flow of inactive gas. In someembodiments, the flow controller can enable relatively constant flowrate of inactive gas through each inactive gas line. In someembodiments, multiple inert gas lines are fed by a common inert gasdistribution channel. As explained herein, in various embodiments, eachinert gas line can include a shutoff valve (which may have an open stateand a closed state) and an adjustable valve, such as a needle valve,that can be set at a plurality of different flow rates. The adjustablevalves can each be kept at a constant setting throughout the depositionprocess in some embodiments.

Furthermore, as explained herein, a bypass line (e.g., a foreline) canconnect to and serve as a bypass around the inactive gas line(s) and thereactant gas line. In some embodiments, the bypass line can also includea shutoff valve (which may have an open state and a closed state) and anadjustable valve, such as a needle valve, that can be set at a pluralityof different flow rates. The adjustable valve along the bypass line canbe set so as to allow some flow of inactive gas through the bypass lineduring dosing. For example, in some embodiments, the adjustable valvecan be set to be significantly more open than the conductance of theflow through the adjustable valve disposed along the inactive gasline(s). In such a manner, during dosing, a portion (e.g., a majority insome embodiments) of the inactive gas can flow along the bypass line,and another portion (e.g., a minority in some embodiments) of theinactive gas can flow through the inactive gas line(s).

In a block 44, the reactant and inactive gases can be fed to a reactorassembly along a feed line. As explained above, the pressure of thereactant vapor can be sufficiently high as to entrain the reactant vaporwith the inert gas as it enters the reactor assembly. In someembodiments, the merged reactant and inert gases can be mixed in amixer, and subsequently delivered to a process chamber by way of aprocess chamber feed line. In other embodiments, the merged gases can befed to the process chamber without an intervening mixer.

Moving to a decision block 45, a decision is made as to whether thereactor assembly is to be purged. If no additional purging is desired,the method 40 ends. If additional purging is desired, the method 40moves to a block 46, in which inactive gas is supplied to the inactivegas line(s) at second flow rate(s) greater than the first flow rate(s).As explained herein, increasing the flow rate during purging canbeneficially reduce processing time and improve the IGV diffusionbarrier. The adjustable valve(s) along the inert gas line(s) can betuned or set such that the desired increase in flow rate(s) is/areachieved during purging.

The method 40 moves to a block 47, in which the inactive gas is fed tothe reactor assembly. The inactive gas can thereby purge the reactorassembly of unused reactant, byproducts, and/or other undesirablematerials. The method 40 returns to the decision block 41 to determinewhether another dose state of another (or the same) reactant is desired.The method 40 can be repeated until the thin film is formed on thesubstrate at the desired thickness and uniformity.

Although the foregoing has been described in detail by way ofillustrations and examples for purposes of clarity and understanding, itis apparent to those skilled in the art that certain changes andmodifications may be practiced. Therefore, the description and examplesshould not be construed as limiting the scope of the invention to thespecific embodiments and examples described herein, but rather to alsocover all modification and alternatives coming with the true scope andspirit of the invention. Moreover, not all of the features, aspects andadvantages described herein above are necessarily required to practicethe present invention.

What is claimed is:
 1. An atomic layer deposition (ALD) devicecomprising: a reactor assembly; a first reactant gas line configured tosupply a first reactant vapor from a first reactant vapor source, thefirst reactant gas line comprising a diffusion barrier portion; a firstinactive gas line configured to supply an inactive gas from an inactivegas source; a first feed line communicating with each of the firstreactant gas line and the first inactive gas line at a first junction tosupply the first reactant vapor and the inactive gas to the reactorassembly; a drain line communicating with the first reactant gas lineupstream of the first junction at a second junction, the diffusionbarrier portion disposed between the first and second junctions; abypass line in fluid communication with the drain line at a thirdjunction and with the first inactive gas line at a fourth junction, thebypass line configured to apply suction to the first reactant gas lineand to the first inactive gas line; a first valve along the firstinactive gas line, the first valve having an open state and a closedstate; a second valve along the first inactive gas line, the secondvalve comprising an adjustable valve configured to adjustably regulategas flow through the first inactive gas line at a plurality of non-zeroflow rates; and a control system electrically connected to one or moreof the first and second valves, the control system configured to: duringa dose state of the ALD device, cause the first and second valves tosupply a first portion of the inactive gas to the first inactive gasline at a first non-zero flow rate and to supply a second portion of theinactive gas to the bypass line; and during a purge state of the ALDdevice, cause the first and second valves to supply a majority of theinactive gas to the first inactive gas line at a second flow rate, thesecond flow rate higher than the first flow rate, such that a pressuredifferential between a first pressure at the first junction and a secondpressure at the second junction during the purge state of the ALD devicecauses the diffusion barrier portion of the reactant gas line to serveas an inert gas valve (IGV) to limit diffusion of the first reactantvapor into the reactor assembly.
 2. The ALD device of claim 1, whereinthe second valve comprises a needle valve.
 3. The ALD device of claim 1,wherein the control system is configured to allow flow through thebypass line during the dose state of the ALD device and to close flowthrough the bypass line during the purge state of the ALD device.
 4. TheALD device of claim 1, wherein the second junction along the firstreactant gas line is upstream of the first junction between the firstreactant gas line and the first inactive gas line.
 5. The ALD device ofclaim 1, further comprising a third valve and a fourth valve along thebypass line, the third valve having an open state and a closed state,the fourth valve comprising an adjustable valve configured to adjustablyregulate gas flow through the bypass line at a plurality of non-zeroflow rates.
 6. The ALD device of claim 1, further comprising: the firstreactant vapor source and the inactive gas source; a second reactantvapor source configured to supply a second reactant vapor to a secondreactant gas line; a second inactive gas line configured to supply theinactive gas from the inactive gas source; a second feed linecommunicating with the second reactant gas line and the second inactivegas line at a fifth junction, the second reactant gas line and thesecond inactive gas line configured to supply the second reactant vaporand the inactive gas to the reactor assembly; a third valve along thesecond inactive gas line, the third valve having an open state and aclosed state; and a fourth valve along the second inactive gas line, thefourth valve comprising an adjustable valve configured to adjustablyregulate gas flow through the second inactive gas line at a plurality ofnon-zero flow rates.
 7. The ALD device of claim 6, wherein the bypassline is in fluid communication with the first and second inactive gaslines by way of an inactive gas distribution line, the bypass lineconfigured to apply suction to the first and second inactive gas linesby way of the inactive gas distribution line.
 8. The ALD device of claim6, wherein the reactor assembly comprises a mixer and a process chamberdownstream of and in fluid communication with the mixer by way of aprocess chamber feed line.
 9. The ALD device of claim 1, furthercomprising a mass flow controller (MFC) configured to regulate gas flowof the inactive gas to the first inactive gas line.
 10. An atomic layerdeposition (ALD) device comprising: a reactor assembly; an inactive gasdistribution line configured to supply an inactive gas from an inactivegas source; a flow controller configured to control an amount of theinactive gas that flows along the inactive gas distribution line; aplurality of reactant gas lines communicating between a plurality ofreactant vapor sources and the reactor assembly, each reactant gas linecomprising a comprising a corresponding diffusion barrier portion; aplurality of inactive gas lines branching from the inactive gasdistribution line downstream of the flow controller, each of theinactive gas lines configured to communicate inactive gas from theinactive gas distribution line to a corresponding feed line at acorresponding first junction between one of the reactant gas lines andthat inactive gas line; a bypass line branching from the inactive gasdistribution line downstream of the flow controller, the bypass lineconfigured to provide fluid communication between the inactive gasdistribution line and a vacuum source and between the plurality ofreactant gas lines and the vacuum source, each of the reactant gas linesin fluid communication with the bypass line by way of a correspondingsecond junction, the diffusion barrier portion of each reactant gas linedisposed between the corresponding first and second junctions; and acontrol system configured to: during a dose state of the ALD device,cause a majority of the inactive gas to flow through the bypass line anda non-zero minority of the inactive gas to flow through a first inactivegas line of the plurality of inactive gas lines; and during a purgestate of the ALD device, cause a majority of the inactive gas to flowthrough the first inactive gas line, such that a pressure differentialalong the diffusion barrier portion of a first reactant gas line of theplurality of reactant gas lines causes the diffusion barrier to serve asan inert gas valve (IGV) to limit diffusion of a first reactant vaporinto the reactor assembly.
 11. The ALD device of claim 10, wherein thecontrol system is configured to close flow through the bypass lineduring the purge state of the ALD device such that all or substantiallyall of the inactive gas flows through the first inactive gas line duringthe purge state.
 12. The ALD device of claim 10, wherein each of theplurality of reactant gas lines includes a drain line leading to thevacuum source, each of the drain lines joining the reactant gas line atthe corresponding second junction to provide fluid communication withthe bypass line, the second junction disposed between the first junctionwith the corresponding inactive gas line and the corresponding reactantvapor source.
 13. The ALD device of claim 10, further comprising: afirst valve along the first inactive gas line, the first valve having anopen state and a closed state; and a second valve along the firstinactive gas line, the second valve comprising an adjustable valveconfigured to adjustably regulate gas flow through the first inactivegas line at a plurality of non-zero flow rates.
 14. The ALD device ofclaim 13, wherein the second valve comprises a needle valve.
 15. The ALDdevice of claim 10, further comprising a third valve and a fourth valvealong the bypass line, the third valve having an open state and a closedstate, the fourth valve comprising an adjustable valve configured toadjustably regulate gas flow through the bypass line at a plurality ofnon-zero flow rates.
 16. The ALD device of claim 10, wherein the reactorassembly comprises a mixer and a process chamber downstream of and influid communication with the mixer by way of a process chamber feedline.
 17. The ALD device of claim 10, further comprising a mass flowcontroller (MFC) configured to regulate gas flow of the inactive gas tothe first inactive gas line.
 18. An atomic layer deposition (ALD) devicecomprising: a reactor assembly; a first reactant gas line configured tosupply a first reactant vapor from a first reactant vapor source, thefirst reactant gas line comprising a diffusion barrier portion; a firstinactive gas line configured to supply at least a first portion of aflow of an inactive gas from an inactive gas source during a purge stateof the ALD device and during a dose state of the ALD device; a firstfeed line communicating with each of the first reactant gas line and thefirst inactive gas line at a first junction to supply the first reactantvapor and the inactive gas to the reactor assembly; a drain linecommunicating with the first reactant gas line upstream of the firstinactive gas line at a second junction, the diffusion barrier portiondisposed between the first and second junctions; a first valve along thefirst inactive gas line, the first valve having an open state and aclosed state; a second valve along the first inactive gas line, thesecond valve comprising an adjustable valve configured to adjustablyregulate gas flow through the first inactive gas line at a plurality ofnon-zero flow rates; a bypass line in fluid communication with the drainline at a third junction and with the first inactive gas line at afourth junction, the bypass line configured to apply suction to thefirst reactant gas line and to the first inactive gas line, the bypassline configured to receive at least a second portion of the flow of theinactive gas from the inactive gas source; a vacuum pump configured toapply a suction force to at least one of the bypass line and the drainline; a third valve and a fourth valve along the bypass line between thefourth junction and the vacuum pump; and a control system configured tocontrol one or more of the first, second, third, and fourth valves tocause, in a purge state of the ALD device, a majority of the flow of theinactive gas from the inactive gas source to flow through the inactivegas line and a minority of the flow of the inactive gas from theinactive gas source to flow through the bypass line to at least in partcreate a pressure differential along the diffusion barrier portion suchthat, during the purge state of the ALD device, the diffusion portion ofthe first reactant gas line serves as an inert gas valve (IGV) to limitdiffusion of the first reactant vapor into the reactor assembly.
 19. TheALD device of claim 18, wherein the third valve has an open state and aclosed state, the fourth valve comprising an adjustable valve configuredto adjustably regulate gas flow through the bypass line at a pluralityof non-zero flow rates.
 20. The ALD device of claim 18, wherein thecontrol system is configured to, during a dose state of the ALD device,cause a majority of the inactive gas to flow through the bypass line anda minority of the inactive gas to flow through the first inactive gasline.
 21. The ALD device of claim 18, wherein the control system isconfigured to allow flow through the bypass line during a dose state ofthe ALD device and close flow through the bypass line during a purgestate of the ALD device.
 22. The ALD device of claim 18, wherein thesecond valve comprises a needle valve.
 23. The ALD device of claim 18,wherein the reactor assembly comprises a mixer and a process chamberdownstream of and in fluid communication with the mixer by way of aprocess chamber feed line.
 24. The ALD device of claim 18, furthercomprising a mass flow controller (MFC) configured to regulate gas flowof the inactive gas to the first inactive gas line.
 25. The ALD deviceof claim 18, wherein the control system electrically is connected to oneor more of the first and second valves, the control system configuredto: cause the first and second valves to supply the inactive gas to thefirst inactive gas line at a non-zero first flow rate during a dosestate of the ALD device; and cause the first and second valves to supplythe inactive gas to the first inactive gas line at a second flow rateduring the purge state of the ALD device, the second flow rate higherthan the first flow rate.
 26. The ALD device of claim 18, furthercomprising: the first reactant vapor source and the inactive gas source;a second reactant vapor source configured to supply a second reactantvapor to a second reactant gas line; and a second feed line configuredto supply the second reactant vapor and the inactive gas to the reactorassembly.